Method and apparatus for calibration of a wireless transmitter

Abstract

When an installed wireless remote unit is operating in the field, routine operation is interrupted to enter a calibration mode. In calibration mode, the compression point of a circuit element is determined by applying a series of different drive levels to the circuit element. Based upon the determination of the compression point, a maximum transmission point is selected for the remote unit. Upon resumption of normal operation, the remote unit uses the maximum transmission point to limit the signal power level transmitted over the wireless link. As time passes or operating conditions change, the calibration process is re-executed.

What is claimed is:  
     
         1 . A method of calibrating transmission circuitry of an installed communication unit, comprising the steps of: 
 interrupting routine operation;    generating a driving signal at a first level which drives a circuit element into saturation;    measuring a first signal power level produced by said circuit element;    setting said level of said driving signal to a second level that is lower than said first driving signal level;    measuring a second signal power level produced by said circuit element;    comparing said first signal power level to said second signal power level; and    if said second signal power level is less than said first signal power level by more than a predetermined amount, using said second driving signal level as a maximum drive level for said circuit element upon resuming routine operation.    
     
     
         2 . The method of calibrating transmission circuitry of  claim 1 , wherein said step of interrupting routine operation is executed in response to the passage of time.  
     
     
         3 . The method of calibrating transmission circuitry of  claim 1 , further comprising the step of transmitting an output of said circuit element within a frequency bandwidth associated with reception at a unit which houses said circuit element.  
     
     
         4 . An apparatus for calibrating transmission circuitry of an installed communication unit, comprising: 
 means for interrupting routine operation;    means for generating a driving signal at a first level which drives a circuit element into saturation;    means for measuring a first signal power level produced by said circuit element;    means for setting said level of said driving signal to a second level that is lower than said first driving signal level;    means for measuring a second signal power level produced by said circuit element; and    means for comparing said first signal power level to said second signal power level, and, if said second signal power level is less than said first signal power level by more than a predetermined amount, using said lower value as a maximum drive level for said circuit element upon resuming routine operation.    
     
     
         5 . The apparatus for calibrating transmission circuitry of  claim 4 , further comprising means for measuring a passage of time and interrupting routine operation in response to a passage of a predetermined amount of time.  
     
     
         6 . The apparatus for calibrating transmission circuitry of  claim 4 , further comprising means for transmitting a signal produced by said circuit element within a frequency bandwidth that enables signal reception at a unit which houses said circuit element.  
     
     
         7 . A method of limiting the output power of a wireless unit, comprising the steps of: 
 interrupting routine operation of an installed communication unit;    selecting a maximum transmission point for said installed communication unit by applying a series of different drive levels to a circuit element within the installed communication unit to determine a compression point of the circuit element; and    resuming routine operation using said maximum transmission point to limit a transmission power of said installed communication unit    
     
     
         8 . The method of calibrating transmission circuitry of  claim 7 , wherein said step of selecting said maximum transmission point for said installed communication unit further comprises the step of measuring a series of relative signal power levels produced by said circuit element.